Rail vehicles, produced in integral construction, often have a baseplate which is constructed as a hollow extruded framework section and extends in the longitudinal direction of the vehicle. For the underfloor attachment of appliances, C-shaped profile fittings are molded onto these hollow profiles, into which fittings there are inserted clamping straps with projecting, welded-in threaded rods. In order to avoid the limbs of the C-shaped profile fitting being spread apart when a nut screwed onto the threaded rod is tightened, a U-shaped rail is pushed over the threaded rods from the outside. This attachment can only transmit relatively low forces in the longitudinal direction of the hollow profile. This is disadvantageous, in particular in rail vehicles, because, in this case, accelerations of up to 5 g can occur in the longitudinal direction of the vehicle during manoeuvring.